1. Field of the Invention
The present invention relates to a wireless transceiver device, and more particularly, to a wireless transceiver device and related devices for providing optimal performance over wireless transmission powers, wireless reception sensitivities, and call current consumptions of different frequency bands.
2. Description of the Prior Art
With rapid development of wireless communications technologies, lightweight, convenient mobile phones have already dramatically altered the way people communicate with each other. Through use of mobile phones, people can conduct voice or data interaction anytime, anyplace. The prior art has already developed many different mobile communications systems according to different communications technologies, such as a Global System for Mobile Communications (GSM), a Code Division Multiple Access (CDMA) communications system, a Wideband Code Division Multiple Access (WCDMA) communications system, a Personal Digital Cellular (PDC) system, and a Personal Handyphone System (PHS), etc.
Generally speaking, different mobile communication systems do their best to avoid sharing operation frequency bands with all other communications systems. For example, GSM can be divided into 900 MHz, 1800 MHz, 850 MHz, and 1900 MHz GSM based on their respective operating frequency bands. The 900 MHz GSM (GSM900) performs reception in a frequency band from 925.2 MHz to 959.8 MHz, and transmission in a frequency band from 880.2 MHz to 914.8 MHz. The 1800 MHz GSM, or Digital Communication System (DCS1800) performs reception in a frequency band from 1805.2 MHz to 1879.8 MHz, and transmission in a frequency band from 1710.2 MHz to 1784.8 MHz. The 850 MHz GSM (GSM850) performs reception in a frequency band from 869 MHz to 894 MHz, and transmission in a frequency band from 824 MHz to 849 MHz. The 1900 MHz GSM, or Personal Communication System (PCS1900) performs reception in a frequency band from 1930 MHz to 1990 MHz, and transmission in a frequency band from 1850 MHz to 1910 MHz.
When designing a single-frequency mobile communications device, a designer may design a mobile communications device according to characteristics such as the operation frequency band, bandwidth, signal transmission and reception power, etc. of the corresponding mobile communications system. However, when the mobile communications device is capable of operating in multiple frequency bands corresponding to different mobile communications systems, more factors must be taken into account, and difficulty of the design increases. For example, in order to reduce size and cost of the mobile communications device, a multiple frequency band antenna will typically replace multiple single-frequency antennas. In this situation, achieving optimal voltage standing wave ratio (VSWR) or reflection coefficient for every frequency band becomes dramatically more difficult.
Please refer to FIG. 1, which is a diagram of a wireless radio frequency circuit 10 traditionally utilized in the GSM850, GSM900, DCS1800 and PCS1900 systems. The wireless radio frequency circuit 10 comprises an antenna 100, an antenna matching circuit 102, and an antenna switch module (ASM) 104. The ASM 104 is formed of a duplexer, switches, and filters, and is utilized for switching output of signals TX_GSM850, TX_GSM900, TX_DCS1800 and TX_PCS1900, or reception of signals RX_GSM850, RX_GSM900, RX_DCS1800 and RX_PCS1900 according to a control signal generated by a radio frequency signal processing unit (not shown in FIG. 1). The antenna matching circuit 102 is utilized for matching impedance of all frequency bands to an ideal 50 Ohms. In other words, taking a test point TP as a benchmark, the ASM 104 on the right half of the test point TP should be designed to 50 Ohms, and the antenna 100 and the antenna matching circuit 102 on the left half of the test point TP must achieve 50 Ohm impedance matching for each frequency band.
In the prior art, when designing the wireless radio frequency circuit 10, after finishing design of the radio frequency processing unit, the designer needs to insert the corresponding antenna 100 into the wireless radio frequency circuit 10, test the VSWR and reflection coefficient of the antenna 100 through a network analyzer, and then modify the shape of the antenna 100 and the characteristics of the antenna matching circuit 102 to achieve the optimal VSWR and reflection coefficient. Then, Total Radiation Power (TRP) and Total Isotropic Sensitivity (TIS) are tested in a 3D microwave darkroom to evaluate isotropic transmission and reception abilities of the mobile communications device.
Modifying the shape of the antenna 100 and the characteristics of the antenna matching circuit 102 according to the VSWR and reflection coefficient is a typical design flow. However, a tradeoff must necessarily occur when only one antenna and one antenna matching circuit are utilized in multiple frequency mobile communication devices of the prior art, making it difficult to meet the requirements for all frequency bands simultaneously. At the same time, impedance modification for low frequency bands and high frequency bands are often at ends with each other, making design difficult.
For example, please refer to FIGS. 2 and 3, which are a Smith diagram and VSWR diagram for a tri-band GSM antenna, utilized for the GSM900, DCS1800, and PCS1900 mobile communications systems. In FIGS. 2 and 3, frequency spectrums corresponding to points 1 to 3 belong to the GSM900 frequency band, points 4 to 6 belong to the DCS1800 frequency band, and points 6 to 8 belong to the PCS1900 frequency band. It can be seen from the VSWR diagram in FIG. 3 that GSM900 shows the narrowest band, DCS1800 the second narrowest, and PCS1900 a wider bandwidth. And from the Smith diagram in FIG. 2, it can be seen that the frequency points of GSM900 are distributed most broadly. In other words, for the narrowest bandwidth, the frequency points are spread widest, such that the low, mid, and high frequency TRP, TIS, and call current consumption in the GSM900 frequency band are harder to cover simultaneously.
Simply speaking, the major factor making design for multiple frequency bands in mobile communications devices difficult is severe limitation on the volume of the internal antenna, which causes a problem of insufficient bandwidth. Further, employment of only one antenna matching circuit to cover the needs of all frequency bands will never be sufficient, and performance in one or more frequency bands will suffer, and the optimum antenna impedance point for each frequency band is different, making it likely that each frequency band will exhibit narrow bandwidth. The impedance at some points is not even close to 50 Ohms, which also causes the problem of poor TRP and TIS. Thus, the wireless radio frequency characteristics in each frequency band are unable to be optimized. When the impedance adjustment tradeoff between low frequency bands and high frequency bands is added in, design difficulty increases even more.